Japanese burdock roots were extracted with aqueous methanol solution. A compound having the inhibitory activity of angiotensin I-converting enzyme (ACE)[EC 3.4.15.1] was purified and identified as nicotianamine, (2S, 3’S, 3”S)-N-[N-(3-amino-3-carboxypropyl)-3-amino-3-carboxypropyl]azetidine-2-carboxylic acid. The compound content in burdock roots and related food products were determined. Data revealed that burdock root is a good source of nicotianamine (NA).